1. Field of the Invention
The present invention relates to markers. More particularly, the present invention relates to luminescent markers.
2. General Background of the Invention
Luminescent semiconductor quantum dots (QDs) have been intensely studied due to their unique optical properties, including sharp emission spectra with full width at half-maximum (fwhm) as narrow as 25 nm, high photostability, and tunable size dependent emission peaks.1-5 Incorporation of luminescent semiconductor quantum dots into nanospheres has been explored as a way to prepare bright biological labels and functional composite luminescent materials. For example, Barbera-Guillem successfully encapsulated luminescent CdSe QDs and other metal oxide nanocrystals in nanometric liposomes for potential biological labeling applications.6 Rogach et al. encapsulated CdSe QDs in 40-80 nm silica nanospheres and proposed to use them as building blocks to form 3D colloid crystal microstructures.7 Moffitt et al. encapsulated CdS QDs in water-soluble block copolymers to form large compound micelles (LCM) that averaged 65 nm in diameter.8 
Electrostatic interactions of polyelectrolytes have been widely applied in layer-by-layer procedures to prepare thin films since Decher et al. introduced this unique technique in the early 1990s.10-11 Using this technique, Anai et al. successfully incorporated the highly charged protein avidin into a thin film and used it to immobilize biotinylated molecules.12 Caruso et al. immobilized enzymes on the surface of polystyrene microspheres to fabricate micrometric biocatalyst carriers using the same layer-by-layer approach.13 Goldman et al. prepared bioinorganic conjugates by using negatively charged CdSe—ZnS QDs and positively charged avidin. They used these new particles for luminescence immunoassay applications.14 In their study, the concentrations of QDs and avidin were limited to minimize aggregation due to electrostatic attractions.
The following U.S. Patents are incorporated herein by reference:    6,773,823 Sequential synthesis of core-shell nanoparticles using reverse micelles    6,699,723 Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes    6,630,307 Method of detecting an analyte in a sample using semiconductor nanocrystals as a detectable label    6,548,171 Fluorescent nanocrystal-embedded microspheres for fluorescence analyses    6,447,887 Electrostrictive and piezoelectric thin film assemblies and method of fabrication therefor    6,322,901 Highly luminescent color-selective nano-crystalline materials.
The following articles (and all references mentioned herein) are incorporated herein by reference:    Decher, G.; Hong, J. D. Makromol. Chem. Macromol. Symp. 1991, 46, 321;    Decher, G.; Hong, J. D.; Schmitt, J. Thin Solid Films 1992, 210/211, 831;    Caruso, F.; Trau, D.; Mohwald, H.; Renneberg, R.; Langmuir 2000, 16(4), 1485;    Goldman, E. R.; Balighian, E. D.; Mottoussi, H.; Kuno, M. K.; Mauro, J. M.; Tran, P. T.; Anderson, G. P. J. Am. Chem. Soc. 2002, 124, 6378.